Work machines, such as mining trucks, typically include a left axle, a right axle, and a differential assembly which mechanically couples the right and left axle. The differential assembly allows the right and left axles to rotate at different speeds relative to one another as the work machine is driven in a curved path.
The differential assembly typically includes a number of side gears and pinion gears enclosed in a differential housing. Each pinion gear is mounted on a roller bearing assembly, which is in turn mounted on a sleeve. The sleeve (with the roller bearing assembly and the pinion gear mounted thereon) is then disposed around a shaft of a spider structure. The spider structure is then positioned in, and secured to, the differential housing such that each pinion gear is positioned relative to a side gear so that the pinion gear meshes properly with the side gear.
A problem with the above described arrangement is that the position of the pinion gear relative to the side gear is determined by a relatively large number of mechanically coupled parts. For example, the positioning of the pinion gear relative to the side gear is determined to some degree by each of the following components; the differential housing, the spider structure, the roller bearing assembly, and the sleeve. As a result, the tolerances of each of the aforementioned components must be carefully controlled in order for the pinion gear to be positioned properly. Having to carefully control the tolerances of the aforementioned components increases the manufacturing cost of the differential assembly.
Another problem with the above described arrangement is that there is a limited amount of space available in the interior of the differential housing. As a result, the more components placed in the differential housing the smaller each component must be. For example, the above described arrangement requires the shaft of the spider structure to have a smaller circumference so the housing can accommodate the additional space taken up by the sleeve. The smaller spider structure shaft is more susceptible to cracking under the loads it is subjected to during the use of the work machine which increases maintenance costs of the work machine.
What is needed therefore is a differential assembly which overcomes one or more of the above-mentioned drawbacks.